SPECIFIC HEATS AND DISPERSION CURVES FOR CsCl ON THE BASIS OF THE SHELL MODEL

1967 ◽  
Vol 45 (10) ◽  
pp. 3339-3346 ◽  
Author(s):  
G. P. Srivastava ◽  
B. Dayal
Keyword(s):  
Specific Heat ◽  
Shell Model ◽  
Lattice Dynamics ◽  
Cesium Chloride ◽  
Dispersion Curves ◽  
Experimental Results ◽  
Fair Agreement ◽  
Chloride Crystal ◽  
Specific Heats ◽  
Positive Ions

The shell model of Dick and Overhauser as developed by Cochran and Woods el al. has been applied to study theoretically the lattice dynamics of a cesium chloride crystal. The polarizabilities of both negative and positive ions have been taken into account in this treatment. The charges on the shells of the two ions come out to be of different magnitude. It is seen that the theoretical specific-heat variation with temperature based on this model is in fair agreement with experimental results in the range for which they have been obtained. The theoretical dispersion curves in the three symmetry directions are also given.

Shell-Model Lattice Dynamics of CsCl, CsBr, and Csl

1972 ◽  
Vol 50 (2) ◽  
pp. 122-128 ◽  
Author(s):  
C. Carabatos ◽  
B. Prevot
Keyword(s):  
Shell Model ◽  
Nearest Neighbor ◽  
Alkali Halides ◽  
Cesium Chloride ◽  
Cesium Iodide ◽  
Frequency Distributions ◽  
Positive Ions ◽  
Cesium Bromide ◽  
Theoretical Predictions ◽  
Model Lattice

Detailed calculations are presented for the frequency distributions and dispersion curves of the three cesium-chloride-structure alkali halides: cesium chloride, cesium bromide, and cesium iodide. In the shell model applied to the study, the polarizabilities of both negative and positive ions have been taken into account as well as the simplified next nearest neighbor interactions. Theoretical predictions and experimental data are in agreement.

An extended three-body force shell model for the lattice-dynamics of ionic crystals

1976 ◽  
Vol 349 (1658) ◽  
pp. 289-308 ◽  
Keyword(s):  
Shell Model ◽  
Lattice Dynamics ◽  
Significant Contribution ◽  
Body Force ◽  
Cesium Chloride ◽  
Dynamical Matrix ◽  
Ionic Crystals ◽  
Range Overlap ◽  
Dynamical Description ◽  
Three Body

An extended three-body force shell model (e. t. s. m.) for the dynamics of ionic crystals of cesium chloride structure has been developed by reformulating the original t. s. m. The dynamical matrix of the model consists of the long-range Coulomb and three-body interactions and short-range overlap repulsions effective up to the second-neighbours. The off-diagonal elements of this matrix along symmetry directions contain a completely new term having significant contribution for unequal shell charges. The long-wave aspects of e. t. s. m. have been explored to describe the elastic and dielectric behaviour of the crystals. The adequacy of e. t. s. m. to describe the lattice dynamics has been investigated by applying it to the case of thallous bromide (TIBr). The overall agreement between theoretical and experimental results seems to be encouraging and gives some confidence to regard it as an appropriate model for the dynamical description of ionic crystals.

Anharmonic Phonons in B.C.C. 4He

1972 ◽  
Vol 50 (11) ◽  
pp. 1152-1155 ◽  
Author(s):  
H. R. Glyde ◽  
F. C. Khanna
Keyword(s):  
Lattice Dynamics ◽  
Reasonable Agreement ◽  
Phonon Frequency ◽  
Frequency Dispersion ◽  
Dispersion Curves ◽  
Experimental Results ◽  
Matrix Approach ◽  
T Matrix

A T-matrix approach is used to calculate lattice dynamics of b.c.c. 4He. The phonon frequency dispersion curves and phonon group widths are in reasonable agreement with the experimental results of Osgood et al.

Lattice dynamics of heavy rare-gas solids

1969 ◽  
Vol 47 (6) ◽  
pp. 617-625 ◽  
Author(s):  
N. P. Gupta ◽  
R. K. Gupta
Keyword(s):  
Iterative Method ◽  
Specific Heat ◽  
Lattice Dynamics ◽  
Reasonable Agreement ◽  
Zero Point ◽  
Central Force ◽  
Experimental Results ◽  
Rare Gas ◽  
Buckingham Potential ◽  
Phonon Spectra

Phonon spectra, dispersion curves, and the specific heat of frozen argon, krypton, and xenon have been studied using a quasiharmonic central force rigid-atom model with interactions up to eighth neighbors. The effect of zero-point vibration is included by an iterative method and a modified Buckingham potential is used. There is reasonable agreement between theoretical and experimental results. A number of possibilities for the improvement of results have been discussed.

scholarly journals LATTICE DYNAMICAL STUDY OF TITANIUM (TI) BY USING CGW-VTBFS MODEL

2021 ◽  
Vol 9 (07) ◽  
pp. 124-129
Author(s):  
U.C Srivastava ◽  
◽  
Shyamendra Pratap Singh ◽  
Keyword(s):  
Experimental Data ◽  
Specific Heat ◽  
Shell Model ◽  
Body Force ◽  
Phonon Dispersion ◽  
Dispersion Curves ◽  
Dynamical Study ◽  
Phonon Dispersion Curves ◽  
Phonon Dynamics ◽  
Experimental Values

In measurements of the phonon dynamics of bcc Titanium (Ti), In the present paper we have reported the lattice dynamical calculations which are performed by using the Clark-Gazis-Wallis (CGW) and Van der Waalsthree body force shell model (VTBFS).The theory is used to compute the phonon dispersion curves(PDC), the Specific heat variation &frequency distribution with the used temperature. The frequencies along the symmetry directions have plotted against the wavevector to obtain the phonon dispersion curves(PDC)from the present models, with the help of available experimental values. The obtained results are agreed well with experimental data.

ON THE SPECIFIC HEAT OF SOLIDS AT LOW TEMPERATURES

1957 ◽  
Vol 35 (7) ◽  
pp. 799-810 ◽  
Author(s):  
T. H. K. Barron ◽  
J. A. Morrison
Keyword(s):  
Specific Heat ◽  
Low Temperatures ◽  
Noble Metals ◽  
Theoretical Models ◽  
Experimental Results ◽  
Continuum Approximation ◽  
Low Frequencies ◽  
Specific Heats ◽  
Additional Information ◽  
The Continuum

The temperature dependence of the specific heat of solids at very low temperatures is examined, using theoretical models and certain recent experimental results. The temperature region over which the continuum approximation (Cν = aT3) is strictly reliable is shorter than has often been supposed, and the series expansion Cν = aT3 + bT5 + cT7 + … is needed for the analysis of accurate experimental results. For insulators θ0 can best be estimated from measured specific heats by plotting Cν/T3 versus T2; the result is a curve whose intercept at T2 = 0 gives the coefficient of T3 (and hence θ0), and whose slopeand curvature give additional information about the vibrational spectrum at low frequencies. For metals the usual plot of Cν/T versus T2 can be used, but here again neglect of curvature may lead to errors in the estimates of γ and θ0. A brief discussion is given of the low temperature specific heats of a number of solids for which suitable data are available: potassium chloride, lithium fluoride, white tin, tungsten, the noble metals, and elements of diamond structure.

Linear augmented-plane-wave frozen-phonon calculation, shell-model lattice dynamics, and specific-heat measurement of SnO

1999 ◽  
Vol 60 (21) ◽  
pp. 14496-14499 ◽  
Author(s):  
S. Koval ◽  
R. Burriel ◽  
M. G. Stachiotti ◽  
M. Castro ◽  
R. L. Migoni ◽  
...  
Keyword(s):  
Plane Wave ◽  
Specific Heat ◽  
Shell Model ◽  
Lattice Dynamics ◽  
Specific Heat Measurement ◽  
Heat Measurement ◽  
Augmented Plane Wave ◽  
Model Lattice ◽  
Phonon Calculation

Experimental Study on the Specific Heat Capacity Measurement of Water-Based Al2O3-Cu Hybrid Nanofluid by using Differential Thermal Analysis Method

2019 ◽  
Vol 15 ◽  
Author(s):  
Andaç Batur Çolak ◽  
Oğuzhan Yıldız ◽  
Mustafa Bayrak ◽  
Ali Celen ◽  
Ahmet Selim Dalkılıç ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Thermophysical Properties ◽  
Volume Concentration ◽  
Pure Water ◽  
Heat Capacity Measurement ◽  
Experimental Results ◽  
Hybrid Nanofluid ◽  
Capacity Measurement

Background: Researchers working in the field of nanofluid have done many studies on the thermophysical properties of nanofluids. Among these studies, the number of studies on specific heat are rather limited. In the study of the heat transfer performance of nanofluids, it is necessary to increase the number of specific heat studies, whose subject is one of the important thermophysical properties. Objective: The authors aimed to measure the specific heat values of Al2O3/water, Cu/water nanofluids and Al2O3-Cu/water hybrid nanofluids using the DTA method, and compare the results with those frequently used in the literature. In addition, this study focuses on the effect of temperature and volume concentration on specific heat. Method: The two-step method was used in the preparation of nanofluids. The pure water selected as the base fluid was mixed with the Al2O3 and Cu nanoparticles and Arabic Gum as the surfactant, firstly mixed in the magnetic stirrer for half an hour. It was then homogenized for 6 hours in the ultrasonic homogenizer. Results: After the experiments, the specific heat of nanofluids and hybrid nanofluid were compared and the temperature and volume concentration of specific heat were investigated. Then, the experimental results obtained for all three fluids were compared with the two frequently used correlations in the literature. Conclusion: Specific heat capacity increased with increasing temperature, and decreased with increasing volume concentration for three tested nanofluids. Cu/water has the lowest specific heat capacity among all tested fluids. Experimental specific heat capacity measurement results are compared by using the models developed by Pak and Cho and Xuan and Roetzel. According to experimental results, these correlations can predict experimental results within the range of ±1%.

The specific heats of three paramagnetic salts at very low temperatures

1956 ◽  
Vol 237 (1210) ◽  
pp. 395-403 ◽  
Keyword(s):  
Specific Heat ◽  
Absolute Temperature ◽  
Magnesium Nitrate ◽  
Paramagnetic Resonance ◽  
Specific Heats ◽  
Ammonium Alum ◽  
Relaxation Measurements ◽  
Ferric Ammonium ◽  
The Absolute ◽  
Measured Specific Heat

The specific heats of three paramagnetic salts, neodymium magnesium nitrate, manganous ammonium sulphate and ferric ammonium alum, have been measured at temperatures below 1°K using the method of γ -ray heating. The temperature measurements were made in the first instance in terms of the magnetic susceptibilities of the salts, the relation of the susceptibility to the absolute temperature having been determined for each salt in earlier experiments. The γ -ray heatings gave the specific heat in arbitrary units. The absolute values of the specific heats were found by extrapolating the results of paramagnetic relaxation measurements at higher temperatures. The measured specific heat of neodymium magnesium nitrate is compared with the value calculated from paramagnetic resonance data, and good agreement is found.

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